taglib/mpeg/mpegfile.h

/***************************************************************************
    copyright            : (C) 2002, 2003 by Scott Wheeler
    email                : wheeler@kde.org
 ***************************************************************************/

/***************************************************************************
 *   This library is free software; you can redistribute it and/or modify  *
 *   it  under the terms of the GNU Lesser General Public License version  *
 *   2.1 as published by the Free Software Foundation.                     *
 *                                                                         *
 *   This library is distributed in the hope that it will be useful, but   *
 *   WITHOUT ANY WARRANTY; without even the implied warranty of            *
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU     *
 *   Lesser General Public License for more details.                       *
 *                                                                         *
 *   You should have received a copy of the GNU Lesser General Public      *
 *   License along with this library; if not, write to the Free Software   *
 *   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  *
 *   USA                                                                   *
 ***************************************************************************/

#ifndef TAGLIB_MPEGFILE_H
#define TAGLIB_MPEGFILE_H

#include <tfile.h>

#include "mpegproperties.h"

namespace TagLib {

  namespace ID3v2 { class Tag; class FrameFactory; }
  namespace ID3v1 { class Tag; }

  //! An implementation of TagLib::File with MPEG (MP3) specific methods

  namespace MPEG {

    //! An MPEG file class with some useful methods specific to MPEG

    /*!
     * This implements the generic TagLib::File API and additionally provides
     * access to properties that are distinct to MPEG files, notably access
     * to the different ID3 tags.
     */

    class File : public TagLib::File
    {
    public:
      /*!
       * This set of flags is used for various operations and is suitable for
       * being OR-ed together.
       */
      enum TagTypes {
        //! Empty set.  Matches no tag types.
        NoTags  = 0x0000,
        //! Matches ID3v1 tags.
        ID3v1   = 0x0001,
        //! Matches ID3v2 tags.
        ID3v2   = 0x0002,
        //! Matches all tag types.
        AllTags = 0xffff
      };

      /*!
       * Contructs an MPEG file from \a file.  If \a readProperties is true the
       * file's audio properties will also be read using \a propertiesStyle.  If
       * false, \a propertiesStyle is ignored.
       */
      File(const char *file, bool readProperties = true,
           Properties::ReadStyle propertiesStyle = Properties::Average);

      /*!
       * Destroys this instance of the File.
       */
      virtual ~File();

      /*!
       * Returns a pointer to a tag that is the union of the ID3v2 and ID3v1
       * tags. The ID3v2 tag is given priority in reading the information -- if
       * requested information exists in both the ID3v2 tag and the ID3v1 tag,
       * the information from the ID3v2 tag will be returned.
       *
       * If you would like more granular control over the content of the tags,
       * with the concession of generality, use the tag-type specific calls.
       *
       * \note As this tag is not implemented as an ID3v2 tag or an ID3v1 tag,
       * but a union of the two this pointer may not be cast to the specific
       * tag types.
       *
       * \see ID3v1Tag()
       * \see ID3v2Tag()
       */
      virtual Tag *tag() const;

      /*!
       * Returns the MPEG::Properties for this file.  If no audio properties
       * were read then this will return a null pointer.
       */
      virtual Properties *audioProperties() const;

      /*!
       * Save the file.  If at least one tag -- ID3v1 or ID3v2 -- exists this
       * will duplicate its content into the other tag.
       *
       * If neither exists or if both tags are empty, this will strip the tags
       * from the file.
       *
       * This is the same as calling save(AllTags);
       *
       * If you would like more granular control over the content of the tags,
       * with the concession of generality, use paramaterized save call below.
       *
       * \see save(int tags)
       */
      virtual void save();

      /*!
       * Save the file.  This will attempt to save all of the tag types that are
       * specified by OR-ing together TagTypes values.  The save() method above
       * uses AllTags.
       *
       * This strips all tags not included in the mask, but does not modify them
       * in memory, so later calls to save() which make use of these tags will
       * remain valid.  This also strips empty tags.
       */
      void save(int tags);

      /*!
       * Returns a pointer to the ID3v2 tag of the file.
       *
       * This method will return a null pointer if either the file can not be
       * read from.
       *
       * If \a create is false (the default) it will also return a null pointer
       * if there is no valid ID3v2 tag.  If \a create is true it will create
       * an ID3v2 tag if one does not exist.
       *
       * \note The Tag <b>is still</b> owned by the MPEG::File and should not be
       * deleted by the user.  It will be deleted when the file (object) is
       * destroyed.
       */
      ID3v2::Tag *ID3v2Tag(bool create = false);

      /*!
       * Returns a pointer to the ID3v1 tag of the file.
       *
       * This method will return a null pointer if either the file can not be
       * read from.
       *
       * If \a create is false (the default) it will also return a null pointer
       * if there is no valid ID3v1 tag.  If \a create is true it will create
       * an ID3v1 tag if one does not exist.
       *
       * \note The Tag <b>is still</b> owned by the MPEG::File and should not be
       * deleted by the user.  It will be deleted when the file (object) is
       * destroyed.
       */
      ID3v1::Tag *ID3v1Tag(bool create = false);

      /*!
       * This will strip the tags that match the OR-ed together TagTypes from the
       * file.  By default it strips all tags.
       */
      void strip(int tags = AllTags);

      /*!
       * Set the ID3v2::FrameFactory to something other than the default.
       *
       * \see ID3v2FrameFactory
       */
      void setID3v2FrameFactory(const ID3v2::FrameFactory *factory);

      /*!
       * Returns the position in the file of the first MPEG frame.
       */
      long firstFrameOffset();

      /*!
       * Returns the position in the file of the next MPEG frame,
       * using the current position as start
       */
      long nextFrameOffset(long position);

      /*!
       * Returns the position in the file of the previous MPEG frame,
       * using the current position as start
       */
      long previousFrameOffset(long position);

      /*!
       * Returns the position in the file of the last MPEG frame.
       */
      long lastFrameOffset();

    private:
      File(const File &);
      File &operator=(const File &);

      void read(bool readProperties, Properties::ReadStyle propertiesStyle);
      long findID3v2();
      long findID3v1();

      /*!
       * MPEG frames can be recognized by the bit pattern 11111111 111, so the
       * first byte is easy to check for, however checking to see if the second byte
       * starts with \e 111 is a bit more tricky, hence this member function.
       */
      static bool secondSynchByte(char byte);

      class FilePrivate;
      FilePrivate *d;
    };
  }
}

#endif